Two-stage discharging structure for low-temperature drying of sticky materials using steam rotary dryer

Abstract

The utility model relates to drying equipment technical field, concretely relates to two section discharge structures of low temperature drying viscous material of using steam rotary drying furnace, and especially suitable for drying of various salt materials such as ammonium chloride. Including oblique arrangement, rotatable rotary furnace cylinder and the concentric circle arrangement of multiple heat exchange pipes in rotary furnace cylinder, and the finished product discharge port and the return material discharge port are equipped on rotary furnace cylinder, the finished product discharge port is used to take out low temperature finished product, and the return material discharge port is used to take out high temperature return material. The utility model divides furnace body into two sections from furnace head to furnace tail according to the drying condition of material in furnace, the first section finished product section starts from the feeding end of furnace head, and the purpose is to obtain finished product, and the section completes the drying of material, and obtains the product that moisture content meets national standard, the second section return material section, and the purpose is to obtain high temperature return material, and the section continues to heat the material that moisture content is qualified, and the heat carried satisfies the requirement of mixing with wet material.

Description

Technical Field

[0001] This utility model relates to the field of drying equipment technology, and more specifically, to a two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer. Background Technology

[0002] For materials containing only free water, drying requires less energy and at lower temperatures. However, drying viscous materials containing free water necessitates material return to reduce the moisture content to a certain level to prevent material sticking within the furnace. To reduce energy consumption, the material temperature needs to be controlled at the appropriate drying temperature; conversely, to increase the temperature of the mixture, improve its flowability in the furnace head section, and prevent material accumulation, sticking, and scaling that could malfunction the rotary dryer, a higher return temperature is required to provide more heat to the low-temperature, high-humidity section of the furnace head. Therefore, in practical applications, a lower finished product temperature and a higher return temperature are needed, which are contradictory requirements.

[0003] Using a steam rotary kiln to dry ammonium chloride, experiments have shown that when the feed moisture content is 6-7% and the material temperature reaches approximately 75°C, the moisture content of the dried ammonium can be controlled within the national standard of 0.5% in 10-15 minutes. However, when the discharged material at this temperature is mixed with the wet material, the furnace head temperature is too low, leading to poor fluidity, material accumulation, and furnace blockage, preventing normal operation. If the material temperature is further increased, it will result in increased steam consumption and increased energy consumption for cooling the finished product.

[0004] The design and operation of existing steam rotary dry ammonium furnaces prioritize normal equipment operation at the expense of energy efficiency. While increasing the discharge temperature prolongs the operating cycle, it also increases steam consumption and energy consumption for cooling the finished product. Another approach involves removing the finished product from the middle of the furnace, using a discharge hood to remove the low-temperature product and exhaust steam; the return material is removed at the tail end, using a return material discharge hood to remove the high-temperature return material and exhaust steam. Theoretically, this scheme can achieve both low finished product temperature and high return temperature, but it violates the principle of prioritizing return material in rotary kilns. During load fluctuations, insufficient or no return material can occur, leading to furnace blockage. Furthermore, with exhaust from both the furnace center and tail end, the internal pressure is difficult to regulate. Utility Model Content

[0005] This utility model aims to provide a two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer, achieving low-temperature finished product discharge and high-temperature return material discharge, thereby reducing energy consumption while ensuring furnace head temperature and improving equipment operational stability.

[0006] To solve the above-mentioned technical problems, this utility model provides a two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer. The structure includes an inclined, rotatable rotary furnace cylinder and multiple heat exchange tubes arranged concentrically within the cylinder. These heat exchange tubes are connected to a steam inlet device at the furnace tail. The material enters from the furnace head at the high end of the furnace. The rotary furnace cylinder is equipped with a finished product discharge port and a return material discharge port. The finished product discharge port is located in the middle to rear of the furnace and is used to remove the low-temperature finished product. The return material discharge port is located at the furnace tail and is used to remove the high-temperature return material. The finished product discharge port conveys the material to the discharge hood at the furnace tail or furnace head via a spiral tube on the outer wall of the furnace. The return material discharge port discharges the material through the furnace tail discharge hood and is then conveyed to a premixer via a conveying device; or it is conveyed to the furnace head via a spiral tube on the outer wall of the furnace to mix with the wet material.

[0007] This utility model divides the furnace body into two sections from the furnace head to the furnace tail according to the drying condition of the material inside the furnace. The first section is the finished product section, which starts from the feeding end of the furnace head. Its purpose is to obtain the finished product (including the preheating and drying sections). This section completes the drying of the material and obtains a product with a moisture content that meets national standards. The second section is the return material section, which aims to obtain high-temperature return material. This section continues to heat the material with qualified moisture content so that the heat it carries meets the requirements for mixing with the wet material. Beneficial effects

[0008] This invention produces finished products at low temperatures and return materials at high temperatures; this ensures low consumption and provides the necessary heat for the preheating section; the increased furnace head temperature not only increases material flowability but also reduces the water vapor partial pressure in the furnace head steam, thus preventing furnace head corrosion. Meanwhile, the finished product section is a constant temperature drying section to ensure the minimum required drying temperature and save energy. After the material is dried, the return material section continues to heat the material and transfers the heat from the tail end to the feed end through the return material, providing sufficient heat for the preheating of wet material mixing and ensuring the long-term normal operation of the rotary kiln. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the finished product of the self-returning structure of this utility model; Figure 2 This is a schematic diagram of the finished product of the external return material structure of this utility model; Figure 3 This is a schematic diagram of the ammonium chloride drying process of this utility model.

[0010] The attached diagram lists the components represented by each number as follows: 1. Rotary furnace cylinder; 2. Spiral tube; 4. Premixer; 5. Feed screw; 6. Separator; 7. Condensation washing tower; 8. Water storage tank; 9. Moisture-carrying heater; 10. Discharge hood; a. Wet ammonium inlet; b. Return material inlet; c. Premixer tail gas outlet; d. Rotary dryer tail gas outlet; e. Return material outlet; f. Finished product outlet; h. Moisture-carrying inlet; i. Steam inlet; k. Steam condensate outlet; j1. Finished product valve; j2. Return material valve. Detailed Implementation

[0011] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0012] Please see Figures 1-2 As shown, the purpose of this utility model is to provide a two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer. The structure includes an inclined, rotatable rotary furnace cylinder 1, and multiple heat exchange tubes arranged concentrically inside the rotary furnace cylinder 1. The heat exchange tubes are connected to a steam inlet device at the tail of the furnace. The material enters from the furnace head at the high end of the furnace body. The rotary furnace cylinder 1 is provided with a finished product discharge port f and a return material discharge port e. A finished product valve j1 is provided on the discharge port f, and a return material valve j2 is provided on the return material discharge port e.

[0013] The finished product outlet f is located in the middle and rear part of the furnace body and is used to remove low-temperature finished products; the return material outlet e is located at the tail of the furnace body and is used to remove high-temperature return material.

[0014] After the material is dried in the furnace for about 3 to 13 minutes and the moisture content is qualified, part of it is treated as finished product and discharged from the finished product outlet f through the finished product outlet valve j1. The remaining material continues to stay in the furnace for 1 to 10 minutes. After the temperature rises, it reaches the return material outlet e at the tail of the furnace and is discharged through the return material valve j2.

[0015] This invention divides the furnace body into two sections from the furnace head to the furnace tail, based on the drying condition of the material inside. The first section is the finished product section, starting from the feeding end at the furnace head, and its purpose is to obtain the finished product (including preheating and drying sections). This section completes the drying of the material, resulting in a product with a moisture content that meets national standards. The second section is the return material section, which aims to obtain high-temperature return material. In this section, the material with acceptable moisture content is further heated so that the heat carried is sufficient to meet the requirements for mixing with the wet material.

[0016] Specifically, the finished product discharge port f conveys the material to the discharge hood 10 at the furnace tail or furnace head through the spiral tube 2 on the outer wall of the furnace body. Relying on the rotation of the furnace body, the finished product is conveyed to the furnace head or furnace tail for discharge. The length of the finished product section accounts for about 50% to 95% of the total length of the furnace body. At the end of the drying of the finished product section, the finished product discharge port f is located at 1 / 2 to 1 / 13 of the furnace body length from the furnace tail, and at least one is evenly arranged along the circumference of the rotary furnace cylinder 1. The finished product discharge port f is evenly arranged along the rotary furnace cylinder 1 and extends radially from the furnace body wall into the furnace body as the finished product furnace discharge pipe. Depending on the furnace size and structure, the radial depth of the finished product furnace discharge pipe can extend from the outermost heat exchange tube near the rotary furnace cylinder wall to any length between the innermost heat exchange tube and the center of the rotary furnace cylinder.

[0017] The remaining materials in the furnace travel a distance of about 50% to 5% of the furnace length to reach the return material outlet e at the furnace tail. Specifically, the return material outlet e discharges through the furnace tail discharge hood 10. The return material outlet e is located at the tail of the furnace body, and at least one is evenly arranged along the circumference of the rotary furnace cylinder. It is then conveyed to the premixer 4 through a conveying device; or it is conveyed to the furnace head through a spiral pipe on the outer wall of the furnace body to mix with the wet materials. The return material outlet e does not have an in-furnace discharge pipe.

[0018] The finished product furnace discharge pipe is composed of four stainless steel plates, including two tube plates parallel to the heat exchange tubes and two tube plates at 90° to the heat exchange tubes; the tube plates pass through the center of each adjacent heat exchange tube, the heat exchange tubes pass through the openings in the tube plates, and there is a gap between the outer diameter of the heat exchange tubes and the openings in the tube plates.

[0019] When the self-returning material is used, the finished product discharge and the return material discharge are respectively conveyed to the furnace head discharge hood 10 through the spiral tube 2 welded to the outer wall of the rotary kiln body 1. Specifically, the spiral tube 2 is welded to the outer wall of the rotary kiln body 1. The finished product discharge port f and the return material discharge port e are respectively conveyed to the furnace head discharge hood 10 through the spiral tube 2 welded to the outer wall of the rotary kiln body 1. The finished product is output from the discharge hood 10, and the return material directly enters the furnace head mixing section or is output from the discharge hood 10 to the premixer 4 according to the furnace structure.

[0020] If materials are mixed inside the furnace, the returned material will not exit through the discharge hood, but will directly enter the mixing section at the furnace head through the furnace body opening.

[0021] When the external return material is used, the finished product is discharged through the spiral tube 2 welded to the outer wall of the rotary kiln cylinder 1 and transported to the tail discharge hood 10. The returned material enters the discharge hood 10 directly through the tail return port e.

[0022] A spiral tube 2 is welded to the outer wall of the rotary kiln cylinder 1. The finished product discharge port f is conveyed to the tail discharge hood 10 through the spiral tube 2 welded to the outer wall of the rotary kiln cylinder 1.

[0023] It should be emphasized that the outer spiral tube 2 consists of two sets of spiral tubes: one set is the finished product conveying spiral tube, and the other set is the return material conveying spiral tube.

[0024] When finished products and returned materials are simultaneously discharged from the discharge hood 10, the finished product discharge port f and the returned material discharge port e are arranged at intervals along the furnace axial direction inside the discharge hood 10. A baffle plate is provided between the finished product discharge port f and the returned material discharge port e to prevent materials from mixing.

[0025] It should be noted that the finished product outlet f is located in front of the return material outlet e.

[0026] The flow of moisture and materials is either co-current or counter-current. When both the gas outlet and the material outlet are at the furnace head or furnace tail, the material outlet 10 discharges material from the bottom and gas from the top. Although the material outlet is located at the front end of the return material outlet, it also ensures the priority of the return material volume.

[0027] To ensure the normal operation of the rotary kiln, the return material collection point is currently located before the discharge point to prevent the material inside the kiln from emptying. It is important to emphasize that although the discharge port is located before the return material port, a special design prioritizes the return material volume.

[0028] The following will refer to the appendix. Figure 3 The following describes in detail the use of a discharge structure for low-temperature drying of viscous materials using a steam rotary kiln, in conjunction with an example of ammonium chloride drying.

[0029] Wet ammonium and returned material are mixed in premixer 4. Wet ammonium at approximately 15°C is premixed with returned material from return material inlet b in premixer 4. The returned material temperature is between 100°C and 150°C. During mixing, the high-temperature returned material and the low-temperature, high-moisture material directly contact each other for heat and mass transfer. The premixer exhaust outlet c sends 10%–50% of the moisture from the wet ammonium and more than 50% of the ammonia to the exhaust gas treatment system. The mixed material, with a temperature ≥70°C, exits from premixer 4 and enters rotary dryer 1 via feed screw 5.

[0030] Driven by the rotation of the furnace body, the mixture moves from the high feed position to the low tail end inside the furnace while indirectly exchanging heat with steam through the heat exchange tube. After about 3 to 13 minutes, it reaches the finished product outlet of the furnace body and enters the spiral tube 2 on the outer wall of the furnace body through the discharge valve j1. With the rotation of the furnace body, the finished product is sent into the furnace tail discharge hood 10 and out of the finished product outlet f of the discharge hood 10 for subsequent packaging. The remaining qualified materials continue to absorb heat from the steam in the heat exchange tubes in the furnace, raising the temperature. After about 1 to 10 minutes, they reach the furnace return port and enter the furnace discharge hood 10 through the return valve j2. They exit from the return outlet e of the discharge hood 10 and are sent to the premixer 4 through the conveying equipment. They enter through the return inlet b and are fully mixed with the wet material from the wet ammonium inlet a in the premixer 4. Then, they are sent to the rotary kiln 1 for drying by the feed screw 5. The furnace steam generated by the rotary kiln 1 exits through the rotary dryer tail gas outlet d of the furnace head discharge hood 10, and passes through the dry dust collector 6 to remove the entrained dust; the premixer tail gas outlet c of the premixer 4 is connected to the inlet pipe of the separator 6, and enters the dry dust collector 6 together with the tail gas of the rotary kiln 1. After the dust is removed, it enters the condensation washing tower 7 to recover the ammonia. The qualified tail gas is discharged or used as a moisture carrier for reuse. The heated moisture-carrying gas enters the rotary kiln 1 through the moisture-carrying gas inlet h at the furnace head; The steam required for drying in rotary kiln 1 enters through steam inlet i at the tail of the kiln, and the condensate generated after heat exchange exits through steam condensate outlet k, passes through water storage tank 8, and is sent to moisture-carrying gas heater 9 to heat the moisture-carrying gas before it enters the kiln.

[0031] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer, comprising an inclined, rotatable rotary furnace cylinder (1), and multiple heat exchange tubes arranged concentrically within the rotary furnace cylinder (1), wherein the heat exchange tubes are connected to a steam inlet device at the tail of the furnace, characterized in that: The rotary kiln cylinder (1) is provided with a finished product outlet (f) and a return material outlet (e); The finished product outlet (f) is located in the middle and rear part of the furnace body and is used to remove low-temperature finished products; The return material outlet (e) is located at the tail of the furnace body and is used to remove high-temperature return material.

2. The two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer as described in claim 1, characterized in that: The finished product discharge port (f) is evenly arranged in a circumferential direction along the rotary kiln cylinder (1) with no less than one port; The return material outlet (e) is evenly arranged in a circumferential manner along the rotary kiln cylinder (1) with no less than one outlet.

3. The two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer as described in claim 2, characterized in that: The finished product discharge port (f) is evenly arranged along the rotary kiln cylinder (1) and extends into the kiln body to form the finished product discharge pipe inside the kiln.

4. The two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer as described in claim 3, characterized in that: The finished product discharge pipe inside the furnace is composed of four stainless steel plates, including two tube plates parallel to the heat exchange tubes and two tube plates at a 90° angle to the heat exchange tubes.

5. The two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer according to claim 1, characterized in that: The return material outlet (e) is not equipped with an in-furnace discharge pipe.

6. The two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer according to claim 1, characterized in that: The outer wall of the rotary kiln body (1) is welded with a spiral tube (2), and the finished product outlet (f) and the return material outlet (e) are respectively transported to the furnace head discharge hood (10) through the spiral tube (2) welded to the outer wall of the rotary kiln body (1).

7. The two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer according to claim 1, characterized in that: The outer wall of the rotary kiln cylinder (1) is welded with a spiral tube (2), and the finished product discharge port (f) is conveyed to the tail discharge hood (10) through the spiral tube (2) welded to the outer wall of the rotary kiln cylinder (1).

8. The two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer according to claim 6, characterized in that: The finished product outlet (f) and the return material outlet (e) are arranged at intervals along the furnace axis inside the discharge hood (10), and a baffle plate is provided between the finished product outlet (f) and the return material outlet (e).

9. The two-stage discharge structure for low-temperature drying of viscous materials using a steam rotary dryer according to claim 2, characterized in that: The finished product outlet (f) is located in front of the return material outlet (e).

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